How to Sync iPad Apps Such as DevonThink To Go at Work- Bonjour over Bluetooth PAN instead of Ad-Hoc Wi-Fi

24 May 2012filed under: computing, mac

So for most of the two years that I’ve had an iPad, I’ve tried (and
failed) to get DevonThink To Go to sync data in some reasonably
useful manner with DevonThink Pro on my laptop. Set aside for the
moment the litany of complaints that people about the synchronization
in DevonThink To Go failing in a variety of circumstances and assume
that it, at least, works as advertised. The problem is:

DevonThink, like many iPad apps, uses Apple’s service discovery
system “Bonjour” to find the companion computer that it’s trying
to sync with on the network. And Bonjour doesn’t work on many
corporate networks.

Or it doesn’t work between subnets or other LAN
segments. Heck, I’ve even tried to set up “wide-area” Bonjour
using my own domain and routing “discovery” information over the
public Internet. All of this so that you can click “synchronize
with this computer,” having chosen from a dynamically
generated list of suitable mates that the program magically “sees”
on the network. The backup plan? Well, there isn’t one.
It’s Bonjour or nothing.

The standard way of dealing with this issue
is a pain: you set up an ad-hoc Wifi network between your laptop
and iPad. This is hardly the worst thing that’s happened in
the world, but remember: if you’re using the Wifi for your Internet
connection on your laptop, this means taking the laptop off the
‘net every time you want to sync with an iPad app that uses Bonjour.
In fact, this is so noxious, that I’m convinced that it has
driven growth in Dropbox. Dropbox became the defacto standard
for synchronization between iOS apps and other computers simply
because the alternatives, either Bonjour discovery of computers on
the local LAN or drag-n-drop in iTunes, are inconvenient at best.
And Dropbox “just works,” even if it does send your precious
stuff out into the big bad world.

So that was a long lead-up to something that I discovered today:
iPads (any) and iPhones as old as the 3GS support a Bluetooth profile
called PAN, or Personal Area Network. Using PAN, your iOS device
can join the network that your laptop is on, but via the laptop and
in a way that preserves Bonjour. Here’s what you do (only once):

Go to “Preferences->Sharing” on MacOS and turn on Internet Sharing
with “Bluetooth PAN” enabled.

Turn on Bluetooth on both your iOS and MacOS device (e.g. your laptop)

“Pair” the iOS device to the laptop. Use Bluetooth Setup
Assistant on the Mac to pair the iOS device and acknowledge the
pairing on the iOS device itself.

From then on, when you want to sync your iOS application, go to
Bluetooth under iOS General Settings and connect to your laptop.
Both your laptop and the iOS device still have Internet access. But
the iOS device is sharing your laptop’s Internet connection and,
even if your corporate LAN doesn’t support Bonjour, it can still
see one device: the laptop that it’s connected to via Bluetooth.

Now you can go back to that original concern: does synchronization
even work in DevonThink to Go? Well, so far so good for the latest
version, but I’ll not trust it to anything critical…. yet.